The invention relates to a method and a device for evaluating the driving style of a driver of a vehicle when travelling on a network of traffic routes, for example a road network, with a corresponding vehicle such as a road vehicle.
Particularly in road traffic, the continuously increasing volume of traffic is making it difficult to achieve the highest possible level of traffic safety. In this context, modern traffic telematics are becoming increasingly significant. With the telematics, the situation or context in which a vehicle is moving, i.e. both its driving state and the traffic situation in which it finds itself at a particular time, can be detected automatically in increasingly better ways by using vehicle-mounted digital roadmaps in which, in addition to the precise geometry of the route network, safety-related attributes such as pedestrian crossings, road signs, etc. can also be stored, and by using highly precise locating of vehicles and extensive vehicle-mounted sensor systems.
Such detection of driving states and traffic situations is used, for example, to detect the driving style of the driver of the vehicle in order to classify it in a predefined way, such as into a sporty, steady or economic driving style, etc, and adapt it as a function thereof, for example transmission shift characteristic curves, or carry out adjustment of the chassis or warn the driver of the vehicle of a current hazardous situation or directly imminent hazardous situation or against driving limiting values being exceeded in a way which endangers driving safety.
WO 92/03803 A1 describes a method and a device for evaluating a driving style, in which a desirable driving state is determined as a function of the driver behavior and driving state parameters, the driving behavior of the driver is evaluated and this evaluation is output to the driver.
Such warning systems are customary in a wide range of embodiments. In one type of such systems, the profile of the road is determined predictively in particular with respect to bend geometries and intersection geometries and/or the presence of possible obstacles on the route in order to warn the driver of the vehicle against approaching the corresponding hazardous point too quickly, which would endanger safety. The determination of hazardous points in advance can be based here on a digital roadmap, see the Laid-open Application EP 0 819 912 A2, and the Patent EP 0 487 280 B1, or on an image-recording and image-processing system which registers the front area of the vehicle, see U.S. Pat. No. 5,757,949.
A further type of conventional system uses a digital roadmap which is expanded with an additional database. The database contains traffic-safety-related information, for example statistical accident data from which information about accident blackspots is generated and, for example, output in the form of a voice message (as described in U.S. Pat. No. 5,270,708) or safety zones, such as residential areas, schools, etc. in which the drive power of the vehicle, and thus the possible speed, is automatically limited, as disclosed in the Laid-open Application EP 0 745 965 A1. Or, safety-related information is provided, for example in the form of road signs, which is output visually and/or audibly as soon as the vehicle approaches the respective location, as disclosed in U.S. Pat. No. 5,146,219.
A further type of conventional warning system provides for the distance from the vehicle travelling ahead to be determined and the driver then to be warned if the distance drops below a predefinable value, see U.S. Pat. No. 5,410,304.
Furthermore, systems which warn against falling asleep and which sense the movement of the vehicle or the profile of the steering angle and draw conclusions from these as to the state of the driver in particular with respect to his degree of tiredness, are known, see European Patent document EP 0 049 522 B1 and the German Laid-open Application DE 196 30 970 A1.
A general problem of warning systems which warn the driving against imminent hazardous situations is that the gain in safety which can possibly be achieved by them is possibly cancelled out again by the driver through a correspondingly risky driving style as the driver can be tempted to trust the warning system and try to find out the triggering limit of the warning system by more risky driving maneuvers than he would make without a warning system, for example to drive through a bend so quickly that a bend warning system which is present responds. The driver is therefore not particularly stimulated by such pre-warning systems to subject his driving behavior, under his own volition, to specific criteria such as more safe driving with sufficient distance from the limiting range of the vehicle movement dynamics and/or to drive in a way which is favorable in terms of fuel consumption.
The technical problem on which the invention is based is to provide a method and a device for evaluating a driving style which can stimulate a driver of a vehicle to select his driving style, i.e. his driving behavior, at his own volition in such a way that it fulfils predefinable desired criteria, for example with respect to driving in a way which is safe for traffic and/or favorable in terms of fuel consumption.
The invention solves this problem by providing a method and a device for evaluating a driving style in which: (a) the current driving state is continuously sensed by reference to associated driving state parameters, and the current traffic situation is continuously sensed by reference to associated traffic situation parameters, (b) an associated reference driving state which, in the respective traffic situation, represents a driving state which is desirable with respect to a predefinable evaluation criterion, is determined in relation to the respectively sensed current traffic situation, by using a predefinable traffic situation reference driving state relation, and (c) the sensed current driving state being evaluated by comparison with the respectively determined reference driving state in accordance with the evaluation criterion, and one or more corresponding acknowledgement information items relating to the driving style during a respective preceding traffic situation being retrospectively output, wherein at least two groups of acknowledgement information items which are associated with two different values of a predefinable category parameter are predefined as driving style acknowledgement information items which can be output, and an acknowledgement generation criterion is predefined that the amount of acknowledgement information items of the one group which are output during a journey remains larger than the amount of acknowledgement information items of the other group which are output or the amount of acknowledgement information items of the one group which are output has a predefinable relationship with that of the other group.
This method and this device characteristically provide for acknowledgement information relating to the driving style during a preceding traffic situation to be output retrospectively, in particular also as information for the driver of the vehicle relating to how his driving behavior during the preceding traffic situation is to be evaluated in accordance with a predefined evaluation criterion. As evaluation criterion, it is possible in particular to predefine whether, or to what extent, the driving behavior corresponds under the given conditions to a safe driving style which does not endanger traffic, which includes, in addition to other criteria, a sufficient distance from the limiting range of the vehicle movement dynamics. Alternatively, or in addition, other evaluation criteria are possible, for example a driving behavior with the lowest possible fuel consumption.
In order to be able to generate such acknowledgement information, the current driving state and the current traffic situation are continually sensed, a driving state which fits the current traffic situation, i.e. one that is desirable, in accordance with the predefined evaluation criterion is derived as a reference driving state and the current driving state is evaluated by comparing it with the determined reference driving state in accordance with the evaluation criterion. In other words, it is determined whether, and to what extent, the driving state corresponds to the reference driving state or how far it departs from it using the evaluation criterion as a measure of distance. The reference driving state is not necessarily to be understood here in the context of every possible driving state as only a punctual state but rather designates in general an entire range of driving states which, in the respective traffic situation under the predefined evaluation criterion, represent possible setpoint driving states which all fulfil the evaluation criterion equally well. Thus, under the evaluation criterion of a driving behavior which is safe in terms of traffic, the reference driving state can cover all the driving states which may be classified as safe in the respective traffic situation, for example have a sufficient distance from the limiting range of the vehicle movement dynamics.
The acknowledgement information provided by the invention which relates to the driving behavior retrospectively, i.e. relates to the respectively preceding driving behavior, has the fundamental advantage over conventional warning systems which warn of a possible hazardous traffic situation in advance, that they can form an independent motivation for the driver of the vehicle to orient his driving behavior according to the predefined evaluation criterion, for example to select a safe and considerate driving style. As a result of suitable configuration and selection of the acknowledgement information which is output, it is possible for a correct driving behavior which is desirable in terms of the evaluation criterion to be taught by the system, and thus learned by the driver of the vehicle by virtue of the fact that the information is configured or selected in such a way that if the current driving behavior corresponds essentially to the reference driving behavior, then the information positively reinforces the behavior in a targeted fashion. As a result, in most cases it is possible to achieve a relatively larger and longer-lasting change in the driving behavior than is possible through compulsory measures which act negatively, for example threats of punishment or confiscation of a driver's license for a certain time, something which is confirmed by corresponding findings from educational psychology.
The method according to the invention and the device according to the invention contain at least two groups of acknowledgement information items of different categories. The outputting of the acknowledgement information items is configured in such a way that the amount, i.e. the number and/or intensity, of acknowledgement information items of the one group which are output, i.e. of the one category, for the respective evaluation time period which can comprise the entire respective journey or part of a respective journey, of one or more traffic situations which have been coped with, is kept larger than the amount of acknowledgement information items of the other group, or is kept in a predefinable relationship with the amount for the other group. For example, in this configuration of the invention, positive, “praising” acknowledgements on the one hand and negative “rebuking” acknowledgements on the other may be provided, the amount of positive acknowledgements preferably always outweighing the amount of negative acknowledgements even when the overall nature of the driving behavior is less positive, and the amount of negative acknowledgements can, if necessary, be reduced to zero, i.e. there are then only positive acknowledgements. As a result, an overall positive acknowledgement impression for the driver can be produced so that the acknowledgements do not spoil his pleasure in driving, but rather motivate him selectively to adopt the desired, for example safe driving behavior, and encourages him to define his competence as a driver by safe driving behavior, and not risky driving behavior.
In a method and device which is developed according to a preferred embodiment of the invention, the outputting of driving style recommendations is provided, by reference to which recommendations the driver of the vehicle can orient his driving behavior in such a way that it corresponds to the reference driving state which is determined for the respective traffic situation. The driving style recommendations are preferably selected here in such a way that there is a sufficient driving behavior margin, in terms of the evaluation criterion of a high level of traffic safety, for example the recommended driving style has a sufficient safety margin with respect to the limiting range of the vehicle movement dynamics.
A method and device which is developed according to another preferred embodiment of the invention take into account the expected loading on the driver in the directly imminent traffic situation, i.e. for the driver travelling along the route directly ahead in the outputting of information for the acknowledgements and the driving style recommendations, if they are provided, the state of the route being estimated in advance for this purpose and in order to sense the current traffic situation. The information is then output only in time periods in which the driver is not too heavily loaded with the imminent driving tasks so that he can pay sufficient attention to the information items which are output.
One advantageous embodiment of the invention is illustrated in the drawing and will be described below.